Telecommunications Networks and their Scope

Radio Transmission wireless communications technology that transmits voice or data over the air using a lower frequency band than microwaves.
Note: Transmission speeds keep on rising, particularly in the fiber optics area. We are now moving toward a global infrastructure of gigabit-speed fiber optic links relying on digital transmission. In this multimedia environment, data, text, voice, images, and video will travel at speeds of billions of bits per second.
Analog and Digital Communications [Figure 7.8][Slide 7-7]
Most of the lines in the telephone systems of the world at present are analog. Signals are transmitted as continuous waves. This is a satisfactory way to transmit voice, but digital data sent by computers (sequences of pulses representing 0s and 1s) must be converted into an analog signal for transmission over an analog line. The analog data must then be converted back into digital before entering the memory of the receiving computer. The conversion of data from digital form into analog for transmission and then back into digital at the receiving end is done by a pair of interface devices called modems (modulator-demodulator).
Modem-based telecommunications have created a significant bottleneck in an environment where computer and peripheral speeds have increased dramatically. The solution is end-to-end digital communications, in which signals are sent as streams of on/off pulses. Digital lines are capable of much faster communication and digital circuitry is now cheaper than analog. All the new equipment now installed in telephone networks is indeed digital.
Trend: There is a shift toward digital telecommunications is taking place throughout the world. A digital system for telecommunications, called TI carrier, is in wide use in parts of the telephone network.
Future: Integrated Services Digital Network (ISDN) - a completely digital telecommunications network standardized by an international committee. Although ISDN services are available in some areas, including most of the US, worldwide ISDN is not expected to become operational until after the year 2000.